Thyratron



June 24, 1958 KATZBERG 2,840,744

THYRATRON Filed Feb. 21, 1957 FIG. I

FIG. 4

CURRENT I TIME M4 t t;

JESSE KATZBERG INVENTOR.

ATTORNEY United States Patent THYRATRON Jesse Katzberg, Tenafly, N. J.,assiguor, by mesne assignments, to Tung-Sol Electric Inc., Newark, N.1., a corporation of Delaware Application February 21, 1957, Serial No.641,508 5 Claims. Cl. 313-493 This invention relates to a gaseousdischarge device of the type which is triggered by a control electrodeto convert it from a non-conducting condition to a conducting condition.The invention has particular reference to a shield arrangement whichencloses a cathode and a control electrode and is designed to produce adischarge characteristic which is unvarying in the elapsed time betweenthe application of a triggering potential and full conductive currentbetween the anode and cathode.

Many types of thyratrons have been designed and used for many types ofservice. When used in radar circuits it is very important that theelapsed time between the application of a firing potential to thecontrol electrode and the time of full conduction be kept as constant aspossible. In ordinary types of thyratrons conduction may start betweenany part of the cathode emitting surface and the nearest point on theanode. Variations of temperature, ionization within the gas, andcondition of the emitting surface make this time interval variable andconsequently the accuracy of the radar system is reduced. The presentinvention employs a shield which encloses the cathode and permitsconduction only through a narrow slot which is in alignment between thecathode and anode. At one end of the slot the geometry is altered sothat a substantially wider portion exists, this wider portion alwaysproviding passage for the initial discharge between the cathode andanode. Since the discharge always starts at this portion, the triggeringaction is uniform in time duration and the entire radar system is mademore accurate.

One of the objects of this invention is to provide an improved gaseousdischarge device which avoids one or more of the disadvantages andlimitations of prior art arrangements.

Another object of the invention is to provide a gaseous discharge devicewhich has uniform firing characteristics.

Another object of the invention is to provide an improved gaseousdischarge device which may be used in accurate radar systems or in anyother timing arrangement where time delay characteristics are of primeimportance.

Another object of the invention is to insure accuracy of timingcharacteristics in a gaseous discharge device by employing structuralcomponents which may be easily assembled in an accurate manner.

The invention comprises a gaseous discharge device which includes anenvelope containing gas at a reduced pressure and includes a cathode, acontrol electrode, an anode, and a shield. The shield is constructed soas to enclose the cathode and the control electrode and has a slotopening adjacent to the anode, this slot having a substantially uniformwidth for the major portion of its length and a substantially greaterwidth for the remainder of its length. I

For a better understanding of the present invention, together with otherand further objects thereof, reference 2,840,744 Patented June 24, 1958r is made to the following description taken in connection with theaccompanying drawings. a

Fig. l is aside view of the discharge device with parts of the envelopebroken away to show the internal construction.

Fig. 2 is a cross sectional view of the device shown in generally anelongated cylindrical electrode parallel to the sides of the envelope.The control electrode 12 may be in the form of a grid or a pluralityofclosely spaced conductors, however, for the purposes of the presentarrangement the control electrode comprises a single" cylindrical rod inalignment with the cathode and the anode. A shield 14 encloses thecathode and control electrode and is formed as shown with a slot 15 inalignment between the control electrode and the anode. The abovementioned components are held in place within the envelope by insulatingspacers 16 and 17 which are generally made of mica. The electrodes,including the shield, are connected to conductors which are sealed in aportion of the envelope and are connected to conducting pins 18 whichare employed for connection with an external circuit.

Referring now to Fig. 3 it will be noted that the slot 15 which extendsfor a major portion of the length of the shield is terminated at theupper end by a much wider slot 20, this portion of the opening betweenthe cathode and anode being arranged for the start of the conductioncurrent. Because this opening 20 is about three times the width of slot15, the initial conduction always occurs through this opening and isalways initiated at the upper end of cathode 11. As long as the initialdischarge is confined to this path the firing conditions will be moreuniform than if the entire cathode surface were available.

The graph in Fig. 4 illustrates the operation of the device. The graphis plotted between current and time, the firing voltage being applied tothe control electrode at time t During the first time interval,conduction is established between the cathode and the control electrode,this increase in current indicated by line 21, and the end of thisoperation being denoted by t During the second time interval, conductionis established be-' tween the cathode and the anode and ending when fullconduction is established at time 1 The shape of the characteristicduring the second time interval is shown by line 22. The shape of thecharacteristic 22 varies with different gasses and depends upon the easeof ionization of the gas. The characteristic shown in Fig. 4 illustratesthe action of Xenon at a reduced pressure. It has been found that thetime T for one type of tube is equal to .3 microseconds and that thistime varies only .05 microseconds, plus or minus, for a wide range oftemperatures and operating conditions.

If a wide slot of the same width as opening 20 were used, the tube wouldfire with less voltage applied to the control electrode but thevariation in firing time T would be considerably greater. If the entireslot were narrow, the same dimension as slot 15, the firing voltagerequired would be much greater but the same variation in firing timewould obtain. The firing voltage for the structure shown in Fig. 3 isonly slightly greater than the firing voltage for a wide slot and thevariation in necessary to place the wide slot at the end of theshield.-

Any other position will produce the same stable characteristics.

The foregoing disclosure and drawings are merely illustrative of theprinciples of this invention and are not to be interpreted in a'limitingsense. The only limitations are mine determined from the'seo'pe oftheappended claims.

I claim:

1. A gaseous discharge device comprising; an envelope containing gas atareduced pressure and including ,a cathode, a control electrode, ananode, and a shield; said shield enclosing the cathode and the controlelectrode and having a slot opening adjacent to the anode; said slothaving a substantially uniform width for at least sixty percent of itslength and a substantially greater width for the remainder of itslength.

2. A gaseous discharge device comprising; an envelope containing gas ata reduced pressure and including a cylindrical cathode, a cylindricalcontrol electrode, an elongated anode' and a shield; said shieldenclosing the cathode and the control electrode and having a slotopening adjacent to the anode; said slot having a substantially uniformwidth for a least sixty percent of its length and a substantiallygreater width for the remainder of its length.

'3. Agaseous discharge device comprising; an envelope containing gas ata reduced pressure and including a cylindrical cathode, a cylindricalcontrol electrode, an,

elongated anode and a metallic shield, said components positioned insubstantially parallel arrangement; said shield enclosing the cathodeand the control electrode and having a slot opening adjacent to theanode; said slot having a substantially uniform width for at least sixtypercent of its length and a substantially greater width for theremainder of its length.

4. A gaseous discharge device comprising, an elongated cathode, an[anode spaced from and parallel to said cathode, an elongated controlelectrode between said anode and cathode, and a metallic shield whichencloses the cathode and control electrode and having a slot openingadjacent to the anode; said slot having a substantially uniform widthfor at least sixty percent of 'its length and a substantially greaterwidth for the remainder of its length.

5. A gaseous discharge device comprising, an elongated cathode with anemitting surface, an anode spaced from and parallel to said cathode, anelongated control electrode between said anode and cathode, and a metalshield which encloses the cathode and control electrode, the emittingsurface of the cathode being exposed to the anode only through anelongated opening in said shield, said opening being substantiallyco-extensive with the cathode and uniform in width for at least sixtypercent of its length and having a substantially greater width for theremainder of its length.

References Cited in the file of this patent UNITED STATES PATENTS I2,185,852 Klopprogge Jan. 2,1940 2,431,237 Freeman Nov. 18, 19472,770,751 Prager et al Nov'. 13, 1956

